1. Field of the Invention
The present invention relates to an image-erasing apparatus for erasing an image formed, on a medium such as recording paper, with an erasable image-forming material and also relates to an image-erasing method of erasing an image formed, on the medium, with an erasable image-forming material.
2. Related Art
With the recent spread in office automation, the volume of various types of information has significantly increased, and information output has increased accordingly. Outputting on a sheet of paper from an image-forming apparatus such as a printer or a copying machine is well known as a mode of information output. As the amount of information increases, large amounts of sheets of paper as a recording medium have been used. This constitutes a problem in view of resource conservation. In order to recycle the sheets of paper once printed with a printer or a copying machine, large amounts of a bleaching agent and water are needed. The cost of recycling also increases when a large quantity of sheet of paper (which may be called merely paper or papers hereinlater) is used.
An erasable image-forming material is used to form, i.e., print, an image on a sheet of paper. The formed image is erased with an image-erasing apparatus so that the sheet of paper can be returned as a blank paper. In this way, the paper can be reused repeatedly, and therefore, the number of sheets of paper required can be substantially reduced. When the quality of the paper is significantly degraded due to repeated reuse, the paper is recycled. In this way, the total cost of reuse of the paper can be reduced.
Generally, an image-erasing apparatus is an apparatus for erasing an image formed on a recording medium (for example, a sheet of paper) with an image-forming apparatus such as a printer or a copying machine. The image-erasing apparatus includes a printing unit which uses toner or ink made of an erasable image-forming material and an erasing unit for removing the toner or the ink.
Japanese Unexamined Patent Application Publication No. HEI 11-316527 discloses an image-erasing apparatus including a device for contacting a solvent to an erasable image-forming material which develops color on a sheet of paper, and a device for removing the solvent from the paper. The erasable image-forming material includes a color former, a developer, and a decolorizer. The solvent dissolves the developer and the decolorizer. This publication provides an erasable image-forming material, and the image is erased by adding solvent or applying heat to thereby reuse the paper.
Further, in order to widely develop such erasable image-forming material, it is necessary to develop or study materials as well as printers or like using such erasable image-forming material and it is also necessary to develop the image-erasing apparatus suitable for office work.
Japanese Unexamined Patent Application Publication Nos. 2000-28450 and 2002-38039 disclose erasable image-forming materials. The images formed with the erasable materials are erased by a solvent or by the application of heat. These materials make it possible to reuse the paper.
In order for the above-described erasable image-forming materials to be used on a more widespread basis, in addition to the development of the materials and the development of printers and copying machines capable of using such materials, the development of image-erasing apparatuses capable of being used in an office is also necessary.
However, conventional image-erasing apparatuses require a solvent container for storing the solvent used for the erasing and a recovered-solvent container into which used solvent is recovered. In addition, a conventional image-erasing apparatus requires a carrying-in roller and a carrying-out roller for bringing the paper into contact with the solvent, a heat roller and an electronic cooler for controlling the temperature, and chemicals such as an adsorbent. Moreover, a conventional image-erasing apparatus also requires a drive mechanism such as a circulation pump. Therefore, the overall structure of the image-erasing apparatus and the erasing process by using such apparatus are complex. In addition, it is necessary to carefully handle the used solvent for safety.
For this reason, an image-erasing apparatus using the solvent is not suitable for use in an office. Therefore, it is desired to realize an image-erasing apparatus suitable for office work of the structure that does not discharge or harmful substance or pollution such as exhaust gas, requires less installation location, is compact in size, and requires less power.
In the meantime, as a concrete erasing method using the image erasing apparatus for erasing the image formed on the medium such as recording paper, there are provided, for example, a method of using a solvent and a method of utilizing heat, as briefly mentioned hereinbefore. On the other hand, as treating or disposed method, there are provided, for example, a mass treatment method in which papers printed with the erasable image-forming materials are collected from offices or working departments and simultaneously treated, and a dispersion (or separate) treatment method in which papers printed with the erasable image-forming materials are treated separately at portions near printers or copying machines utilized for the printing treatment.
In the case of the mass treatment method, the erasing apparatus becomes large or big in size, which will require a specific room, chamber or building for treatment and in the case of the separate treatment method, a small-sized erasing apparatus is usable, being convenient in usual office work or treatment in office.
Moreover, in the case of using the solvent, the use of volatile organic solvent is not suitable and dangerous for the use in the office or like. In this meaning, the thermal erasing method, using no organic solvent, may be suitable for the erasing apparatus of the image-forming material.
However, the image-forming material erasing method or apparatus mentioned above provides the following undesirable matters.
That is, in the conventional erasing apparatus for the image-forming material, paper as a recording medium is also heated together with the printed image-forming material at the image erasing treatment time. Papers are usually classified into acid papers and neutral papers in accordance with their manufacturing methods. In a usual paper manufacturing process, an ink bleeding-stop agent (sizing agent), such as colophonium, is added, and in order to fix such colophonium to the paper, aluminium sulfate is generally utilized. The aluminium sulfate has a function of reacting to water to thereby generate acid and make the paper as acid paper. Therefore, the paper using the aluminium sulfate is generally called “acid paper”, in which cellulose as fiber of the paper is apt to be damaged, which provides a problem of durability of the paper. In view of this matter, a paper utilizing a neutral material as sizing agent has been used to improve the durability of the paper, which is, on the other hand, called “neutral paper”. In addition, in further consideration of preservation of the paper, such as calcium carbonate is added to neutralize acid in atmosphere to thereby keep weak alkaline property of the paper.
As mentioned above, various chemical treatments have been usually effected to the general papers in their manufacturing process.
Furthermore, the erasable image-forming material is erased by heating a medium such as recording paper on which the image is formed at a predetermined temperature. However, when the sheet of paper is heated, in some cases, the components, such as those mentioned above, contained in the paper may be evaporated and an odor generating substance may be produced, such as, for example, benzaldehyde, octanol, or like. Such odor or odor generating substance will be dispersed at the erasing time in a room in which the erasing apparatus is set. This matter may also constitute an adverse problem if the room is not so wide.